Co-pending, commonly owned application Ser. No. 08-897,435, filed Jul. 21, 1997, entitled "Ballast Circuit for Gas Discharge Lamp," by Louis R. Nerone (the present inventor), David J. Kachmarik, and Michael M. Secen, discloses and claims a ballast for an electrodeless lamp. The ballast includes a d.c.-to-a.c. converter formed of a pair of serially connected switches having opposite conduction modes. For instance, one switch may be an n-channel enhancement mode MOSFET, and the other, a p-channel enhancement mode MOSFET, with their sources interconnected at a common node. This allows a single control voltage applied to the gates, or control nodes, of the MOSFETs, to alternately switch on one MOSFET and then the other.
The foregoing ballast includes, in a resonant load circuit, both an r.f. inductor for generating high frequency fields for energizing the electrodeless lamp, and an inductor selected to set a resonant frequency of operation of the load.
It would be desirable to provide a ballast for an electrodeless lamp which, on the one hand, benefits from the simplicity of switch control obtained by using switches of different, or complementary, conduction types, while, on the other hand, reducing the parts count of the ballast, to reduce ballast cost.